Not applicable.
Various medical diagnostic apparatus require that aspects of a patient""s respiration, such as inspiration volume, be measured. Illustrative of such apparatus are heart rate variability assessment monitors which can be used in the diagnosis and treatment of various disease states.
In certain applications, it is advantageous to have the patient breathe in a particular manner when measuring inspiration volume. As one example, in neuropathy diagnosis, it is desirable that the patient breathe at a predetermined, constant frequency, such as on the order of six breaths/minute, or 0.10 Hz. However, even with specific instructions, it is difficult to ensure that the patient will breathe at the constant, predetermined frequency (i.e., to ensure xe2x80x9cpatient compliancexe2x80x9d with a desired breathing pattern). Further, even if the patient complies closely with the desired breathing pattern, a patient""s breathing often varies between tests, rendering the results of long-term testing less meaningful due to inter-test variability.
In an effort to enhance patient compliance and thus to reduce inter-test variability, some conventional systems include interactive mechanisms by which the patient is instructed to breathe in accordance with a particular pattern. For example, in a monitor sold under the product name HRView(trademark) versions I and II by Boston Medical Technologies, Inc., different audio tones are used to indicate to the patient when to inhale and when to exhale. While this arrangement improves patient compliance and reduces inter-test variability, an even more effective way of ensuring patient compliance with a particular breathing pattern is desirable.
Apparatus and methods for enhancing a patient""s compliance with a predetermined breathing pattern include the use of feedback based on inspiration, or breath flow. Inspiration flow is the rate of breathing over time. A system according to the invention includes a device for measuring the inspiration flow of a patient, a first display on which the patient""s measured inspiration flow is displayed and a second display on which a target inspiration flow is displayed. The system further includes a processor for controlling the first display in response to the measured inspiration flow and for controlling the second display in accordance with a predetermined function. The patient is instructed to breathe so as to cause the measured inspiration flow display to match, or follow the target inspiration flow display.
With this arrangement, patient compliance with a predetermined breathing pattern is achieved in a highly accurate and repeatable manner. This is because modifying one""s breathing to emulate an inspiration flow pattern has been found to be a relatively easy task, for example as compared to emulating an inspiration volume pattern. Further, inspiration flow feedback does not suffer from certain errors, such as may be associated with converting a measured flow signal into a volume signal. Thus, patient feedback based on inspiration flow results in a precise and repeatable matching of actual inspiration flow to a target inspiration flow.
Preferably, each of the first and second displays comprises a corresponding plurality of display elements disposed adjacent to one another in order to facilitate visual comparison. In one embodiment, the display elements are LEDs arranged in the form of a bar graph.
In one embodiment, the processor controls the second, target display portion according to a predetermined mathematical function. Illustrative mathematical functions include a sine wave function, a square wave function, a triangular function, a trapezoidal function, a chirp function or a combination of two or more such functions.
In accordance with a further aspect of the invention, the processor is responsive to the measured inspiration flow for computing the patient""s inspiration volume. In a metronomic deep breathing test, the inspiration volume is used to compute a deep breathing maximum level which is used to prompt the patient to breath to a predetermined percentage of lung capacity. The inspiration volume is further processed to determine the extent to which the patient""s breathing pattern matches the target breathing pattern.
Also described is a method for enhancing patient compliance with a predetermined breathing pattern including the steps of measuring the patient""s inspiration flow, displaying the measured inspiration flow, displaying a target inspiration flow in accordance with a predetermined function, and instructing the patient to breathe in a manner which causes the measured inspiration flow display to match, or follow the target inspiration flow display.
According to a further aspect of the invention, a system for improving patient compliance with a predetermined breathing pattern includes a display for displaying the measured inspiration flow of the patient. The display includes a maximum flow display portion which indicates when the patient""s inhalation flow exceeds a predetermined maximum level and a minimum flow display portion which indicates when the patient""s exhalation flow falls below a predetermined minimum level. Both the predetermined maximum level for inhalation flow and the predetermined minimum level for exhalation flow are functions of the measured inspiration flow of the patient. The display further includes a target inspiration flow portion for displaying a target inspiration flow.
With this arrangement, a patient is provided with an indication that their inspiration flow (i.e., breathing rate) is either too high or too low. In this way, the patient is provided with further guidance in controlling his or her breathing so as to cause the measured inspiration flow to match the target inspiration flow, thereby further enhancing the accuracy and inter-test repeatability of the breathing test. This feature is particularly advantageous when conducting metronomic deep breathing testing for heart rate variability analysis in which the patient is instructed to breath to a predetermined percentage of his or her lung capacity at a predetermined frequency.